Name:	brkl_PercentageOfLoansAndLeasesReceivableToAggregateOutstandingAmountInNewYorkNewJerseyAndOtherNortheasternStates
Namespace Prefix:	brkl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Reflects the percentage of loans and leases receivables to aggregate outstanding amount held in portfolio, prior to deducting deferred income and the allowance for losses on loans and leases.

No definition available.

Name:	brkl_PercentageOfLoansAndLeasesReceivableToAggregateOutstandingAmountInStatesOutsideOfNortheastRegionInUnitedStates
Namespace Prefix:	brkl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the liability for unfunded commitments on extensions of credit to insiders.

No definition available.

Name:	brkl_UnfundedCommitmentsOnExtensionsOfCredit
Namespace Prefix:	brkl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The sum of the carrying amounts, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and for which the transferees are not permitted to sell or re-pledge them to an unrelated party.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Name:	us-gaap_PledgedFinancialInstrumentsNotSeparatelyReportedLoansReceivablePledgedAsCollateral
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6378536&loc=d3e10092-111533